[alsa-devel] OMAP-McBSP driver not allowing suspend/resume

[Dasgupta, Romit]

> As can be seen from the log, both the CORE and PER power domains
> are not going to the suspend state.
> 
> On further debug, I found that McBSP 2 instance belongs to the
> PER domain whereas SDMA belongs to CORE domain. And at least
> McBSP driver (on l-o tip) doesn't allow disabling of the clocks
> unless McBSP instance itself is freed. Because of this, when
> McBSP is stopped after receiving the suspend request, the
> clocks are still ON and the PER domain is not allowed to enter
> to the desired low-power state.
> 

Yes, the McBSP clocks are enabled when the PCM substream is opened and released only when the pcm substream is closed. There are no .suspend/.resume callbacks in the mcbsp driver today. You need to save context of McBSP and disable clocks on suspend and enable clocks and restore context on resume.